Beluga Whale Group Sizes in Cook Inlet, Alaska Based on Observer Counts and Aerial Video
June 30, 2000
Scientists utilize and analyze video recordings to collect more accurate data for beluga whale counts and estimated group sizes. This study also involves annual observer aerial surveys conducted from 1994 to 2000.
Aerial Counts of Beluga Groups Aerial counts were made by pairs of observers tallying beluga whale sightings independently during counting passes (Rugh et al., 2000). A racetrack flight pattern, typically 2–4 km from end-to-end and 1–2 km across, depending on the size of a group, usually allowed two counting passes per circuit around the group, if glare was not a problem (Fig. 1). Start and stop times were precisely noted for each counting pass, and observers graded the conditions during each count (from A to D for excellent to poor). The protocol was to continue this process until each of the observers had made at least four counts under acceptable conditions (A or B). Then observers traded positions, and the process was repeated.
Typically, each group of whales was counted 16 times, four times by four different observers. This method allowed for repeatable, independent counts by four observers with essentially the same presentation of the group and a measure of time spent counting. The number of counts was reduced when groups were small (less than five whales) or dense air traffic prevented staying in the area. Each observer recorded counts independently, and counts were not discussed among observers during the remainder of the project. To further maintain independence, the counts were entered into the database by a colleague who did not participate in the counts, or they were entered only after the survey was completed.
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Roderick C. Hobbs, Janice M. Waite, and David J. Rugh. Published in Marine Fisheries Review, 62(3), 2000.